Lunt LS100MT/B3400 Multi-Purpose (Day/Night) Apochromatic Telescope

The Lunt LS100MT/B3400 is designed for observers who want more than a glimpse of the Sun. Its 100 mm unobstructed aperture provides a substantial increase in resolving power and light-gathering capacity over smaller solar instruments, giving the telescope the optical reach to explore fine structure across the solar disc and around the solar limb.

At the centre of the system is Lunt’s internally mounted H-alpha etalon with Doppler True barometric pressure tuning. Rather than relying on mechanical tilting of the etalon, the pressure tuner allows the observer to adjust the system precisely to the H-alpha wavelength. The current Lunt specification gives the 100 mm Universal an individually verified 0.45 Å single-stack bandpass, designed to isolate the H-alpha wavelength and reveal chromospheric features such as prominences, filaments and active regions.

The additional aperture is particularly valuable when observing fine solar structure. Lunt specifically highlights prominences, surface granulation, active regions and filaments among the features visible through the 100 mm Universal, while the larger aperture also provides the resolving power needed to make the most of good atmospheric conditions.

A B3400 configuration for serious imaging

This version is equipped with Lunt’s B3400 blocking filter, with a large 34 mm clear aperture. Lunt identifies the B3400 as the largest blocking-filter option for its 100 mm and 152 mm systems and specifically recommends it when using a large-format camera or binoviewer. The B3400 is installed inside the focuser rather than in a dedicated blocking-filter diagonal, allowing the telescope to be used with a conventional 2-inch star diagonal for visual observing.

That large illuminated field makes the B3400 configuration particularly attractive to solar imagers who want to work with larger sensors. It also gives the LS100MT considerable flexibility for visual observing with binoviewers and 2-inch accessories.

Premium apochromatic optics

The solar system is built around a professional-grade 100 mm FPL53 ED apochromatic triplet with a 714 mm focal length and f/7 focal ratio. Lunt specifies ion-assisted broadband anti-reflection coatings on the objective. The triplet design is not simply a solar accessory around a basic refractor: when the H-alpha module is removed and the appropriate night-time conversion equipment is fitted, the same optical system becomes a full 100 mm f/7 apochromatic refractor for lunar, planetary, deep-sky and terrestrial observing, as well as astrophotography.

This is an important part of the LS100MT’s value. You are not buying an instrument that spends most of its life waiting for clear nights or solar activity. The telescope can move between high-resolution solar observing during the day and conventional astronomical observing after sunset, making the substantial investment in a 100 mm premium optical system useful across a much wider range of observing.

Built for precise observation and imaging

The 2-inch dual-speed rack-and-pinion focuser incorporates a 10:1 fine-focus reduction and is compatible with the ZWO EAF for motorised focusing. Combined with the 714 mm focal length, this provides a strong platform for both high-resolution solar imaging and conventional astronomical imaging once the telescope has been converted for night use.

The LS100MT is also modular beyond its basic day/night conversion. Lunt lists optional capabilities including additional H-alpha filtering, Calcium-K and white-light configurations, allowing the instrument to be expanded into a broader solar-observing platform.

A high-value premium observing instrument

The LS100MT/B3400 occupies a particularly desirable position for the experienced solar observer: 100 mm of unobstructed aperture, premium FPL53 triplet optics, precision pressure-tuned H-alpha performance and a 34 mm blocking filter in one modular system.

It is an instrument built around the idea that solar observing does not have to be limited to simply seeing whether there is a sunspot today. With 100 mm of aperture and a dedicated narrowband H-alpha system, the observer can spend time studying the changing structure of the solar atmosphere, while the same optical tube remains available for serious night-time astronomy.

For an enthusiast investing in a premium solar telescope, the LS100MT/B3400 therefore offers something particularly valuable: a high-end solar instrument that does not become a single-purpose telescope when the Sun goes down.